Brushless Geared hubmotors: BIG list & details

[Iron Yeti]

I thought I would bump this thread as I have become interested in brushless geared hub motors. I live in a very hilly area and I am thinking my money would better be invested in a geared hub motor.

My understanding is that geared hub motors might be a little bit louder and their gears might need replacing but they are more efficient than non-geared brushless hub motors.

I was planning on going with Crystalyte 408 which is rated at 500W. So would a 250W geared hub motor almost match the performance of a 408 in speed while dominating it in torque?

Recommendations?

[docnjoj]

Yeah well 250 watts is "nominal"! I routinely ran 36 volts at 20-25 amps thru my P2A! I believe we all run higher amps than we think! My motor had to haul 300 lbs of trike and human! I dont have a Cycleanalyst but I use a volt and ampmeter. I think smaller geared motors are the way to go (brushed or brushless) If they can run quiet gears, they rule!
otherDoc

[Iron Yeti]

I've been reading about the BMC Puma geared hub motor but I can't find any information or a website where I can check out the price. Help?

[pwbset]

I can't find any information or a website where I can check out the price. Help?

http://www.texaselectricbikes.com/catalog/brushless-geared-motor-p-163.html

[Iron Yeti]

I wish all these other geared hub motors weren't rear wheel. Regardless, I really want that BMC. I think I might be able to scrape up the extra funds for it, or change my battery configuration since they are more efficient.

Edit: Has anyone bought just the motor from them? What controllers are compatible with it?

[voicecoils]

I wish all these other geared hub motors weren't rear wheel. Regardless, I really want that BMC. I think I might be able to scrape up the extra funds for it, or change my battery configuration since they are more efficient.

Edit: Has anyone bought just the motor from them? What controllers are compatible with it?

The Bafang PMGR (brushless geared) comes in a front hub. That's what I've ordered, and plan to run it at 72v ~30a

[Iron Yeti]

I wish all these other geared hub motors weren't rear wheel. Regardless, I really want that BMC. I think I might be able to scrape up the extra funds for it, or change my battery configuration since they are more efficient.

Edit: Has anyone bought just the motor from them? What controllers are compatible with it?

The Bafang PMGR (brushless geared) comes in a front hub. That's what I've ordered, and plan to run it at 72v ~30a

I actually meant I wish they weren't all front hub.

[voicecoils]

I actually meant I wish they weren't all front hub.

Ahh, got it.

There is a Bafang PMGR rear I think too, you should ask Keywin. See attached. The BMC looks quite nice, has been better tested, but is more costly.

[Iron Yeti]

Where might I contact him?

[voicecoils]

Where might I contact him?

"Keywin Ge" ecrazyman@gmail.com and ask for a quote on what you want and where you're located.

He's on eBay but not everything is listed. I've ordered but not received or tested, so proceed with caution. Knuckles has had good experiences it seeems.

[Mark_A_W]

I actually meant I wish they weren't all front hub.

Ahh, got it.

There is a Bafang PMGR rear I think too, you should ask Keywin. See attached. The BMC looks quite nice, has been better tested, but is more costly.

That's 172mm wide - it aint gunna fit in a 135mm dropout.

[andys]

e-crazyman told me last week his controllers are not fully compatible with the geared hub motors. I asked about the BMC one, and he told me he didn't have a controller that would work right with it.

[andys]

Doug at EV Tech still has some front wheel versions of the BMC geared hub, but doesn't recommend them unless you have a very strong fork and run a beefy torque arm.

[voicecoils]

Thanks for your response andys. I'll edit the BMC post to say that front OR rear can be had. sounds like the fronts are limited in supply.

do you know if the Puma and BMC are identical products? I'd like to keep this thread rolling, with good info

[Knuckles]

It is about time that I clarify some technical issues concerning the Bafang PMGR motor.
...
The ring gear in the hub appears strong and made of steel.

...
The rotor gear (sun gear) looks fairly robust as well (also made of steel).

...
(Edit 6/30/08) The planetary gear set (3 nylon planet gears) does not stay stationary during freewheel. It rotates along with the ring gear during freewheel.
Applying throttle causes the gear set to cease rotating within the motor as torque is applied to the wheel. The gear-set-freewheel-assembly is anchored to the axle by a key pin.

...
Above is the freewheel with the gears removed. The gear-set-freewheel-assembly can spin freely in one direction around the freewheel bearing.
The planet gears spin and translate (the gears move their location during freewheel and are staionary under applied rotor torque) all within the body of the motor.
The planet gears also have sealed bearings. The planet gears are held in place by those little clips.

...
Golly! What's wrong with this gear (actually it kinda looks like a sun god now ... 1960's hippie style)?

This is what happens to the gear if the torque exceeds the yield strength of the nylon gears.
See explanation of why it failed here ... viewtopic.php?f=2&t=4282&p=73746#p73578
Clearly the nylon gears are a very WEAK LINK in this motor design.

But I am not ready to throw the baby out with the bath water quite just yet!

So I plan on fabricating stronger planetary gears at my local gear fabricator shop (we have them here in NY).

Some other interesting tidbits ...
1) There is definitely a freewheel! The rotor only spins when applying torque. The planet gears are either spinng against or rotating with the ring gear.
The wheel freewheel spins with very little " resistance in the forward direction.
2) The motor will NOT run in reverse (it only freewheels in one direction).
3) Shorting the three phase wires completely brakes the motor in reverse direction only.
4) This is a VERY POWERFUL MOTOR! It has no problems at 72V and 30-amps.

The nylon gears will turn to "peanut butter" if you brake the wheel and accelerate the throttle at the same time. E BRAKES ARE ESSENTIAL!

SOLUTION: Simply add one steel gear (or maybe an alloy gear) to the planetary gear set. This is exactly what Keywin and I are planning to do.

BTW ... I am buying plenty of replacement nylon gears too (for sale of course) to all the good planetary folks just in case replacements are needed.
But I just can't wait to get my new MEGA SUPER GEARS fabricated and installed so I can SHRED UP the road with this tiny yet powerful motor!

On a final note ... Just so that we are all on the same page ... My Grubee black motor on my chopper ...
(see ... viewtopic.php?f=6&t=4160#p62316)
... is still more powerful (faster) than the Bafang (same V and amps) regardless of the Bafang gear material.
But the Bafang PMGR is infinitely superior at slower speed with UNSTOPPABLE torque output.

cheers
Knuckles

PS I will have the rear Bafang motor soon ... and put to rest once and for all ... the issue of whether this motor will fit into a rear bicycle drop-out.

Just came in.

[ngocthach1130]

why don't you get a quote on large case of the steel gear? Maybe you can put that as an upgrade option to for the bafang motor purchase. I figure those nylon gear won't last long if we use plug braking on the bafang.

[shinyballs]

Knuckles thanks for clarifying. I cannot get any exact data regarding rpm, some questions -

1. What's the no load rpm from the hub at 72v? I read somewhere around 400 but not sure...
2. How long did the nylon gears last (miles)?
3. Will a stock Crystalyte analog 72v 35Amp fry this motor? I already have one, so might as well use it when I order this motor.

[Ben]

I also have a question and I'm not sure if you know the answer.

Are the rpm/speeds given on the Bafang website no-load speeds or actual speeds?

[Knuckles]

Concerning the nylon gears ...
I have been thinking about these nylon gears.
It occurs to me that the choice of gear material by Bafang may have been determined due to thermal expansion criteria.
In other words, as a gear heats up it will expand (thermal expansion of the gear material).
This thermal expansion might cause the planetary gear system to bind up.
Also. I think the hardness of the nylon changes drastically as a function of temperature. As the nylon heats up it gets very soft.
Once it cools down it hardens up again. Maybe if you never overheat the motor (like my friend did to me), there may never be a problem with the nylon gears.
Yet I often get my DD motors nice and hot when I get a little 'cranky' and go for a 'psycho' ride to blow off some steam.
Replacing the wire harness, however, really seems to help keep the DD motor cool even when I go into 'psycho' e bike mode.
See ... viewtopic.php?f=2&t=4626#p68468

Concerning the no-load rpm ...
I have no way to directly measure the no-load rpm as I have not yet purchased a CA. I guess I could buy a cheap odometer for the fork.
In many ways I don't really care as I just test any motor on a bike and I just see how fast it goes and how responsive it is.
But all motors will have their own unique motor constant (K - rpm/v). But this critical value is rarely reported by a motor manufacturer.
I imagine the K value can also be calculated by knowing the exact construction of any given motor. But I am not a motor design engineer.

Concerning the Bafang Motor Company ...
I recently heard that this company is somewhat unresponsive to requests for design modifications. Hey, sh*t happens.
Time will tell and I am not about to give up on a large manufacturer because they won't listen to me on just a handful of purchases.
Money talks. And I can always just fabricate any gear I want and if it turns out to be superior then I can shove it right back in their faces.
Rome was not built in one day.

Concerning humor ...
I really like riding my e bikes. It is FUN. I also like to think I am a good engineer but I can be arrogant sometimes. Most engineers are arrogant by nature.
I also like to make jokes and goof around. Even more so when it comes to EV. But I also know that EV is critical to the survival of this planet.
Global Warming is real and we MUST stop with the oil and look at solar and other sources of energy or our posterity will be doomed.
EV is the ONLY way for our species to go so what goes on in this forum is very very important.
But I do love to bust balls and goof around too! But I always take care of my clients. Always.

cheers

[shinyballs]

Concerning the nylon gears ...
I have been thinking about these nylon gears.
It occurs to me that the choice of gear material by Bafang may have been determined due to thermal expansion criteria.
In other words, as a gear heats up it will expand (thermal expansion of the gear material).
This thermal expansion might cause the planetary gear system to bind up.
Also. I think the hardness of the nylon changes drastically as a function of temperature. As the nylon heats up it gets very soft.
Once it cools down it hardens up again. Maybe if you never overheat the motor (like my friend did to me), there may never be a problem with the nylon gears.
Yet I often get my DD motors nice and hot when I get a little 'cranky' and go for a 'psycho' ride to blow off some steam.
Replacing the wire harness, however, really seems to help keep the DD motor cool even when I go into 'psycho' e bike mode.
See ... viewtopic.php?f=2&t=4626#p68468

A fix, but still won't solve the heating problem is maybe adding a temp probe in the motor, wired to a switch that automatically cuts-off the power when it reaches a certain temperature? or like a warning red light/beep indicator. I saw this mod one time here but can't find it anymore...

[Knuckles]

Funny. I use a $15 temp probe to measure my NiMH bat pack chargers.
These sell in the supermarket and target too. Easy to install.

But it get's even goofy'r. Replacement gears are like real cheap.

So thus continues the evolution of the EV revolution.

Party On!

[deVries]

Doug at EV tech engineered and designed the geared hub motor over a period of many years. Too bad he didn't patent it, as now the manufacturers have sold his design to others who put their names on them. I have his hub on the rear of a bike and it is an 8 pound torque monster. One thing not mentioned much about these motors, is that they are very efficient. Quite a bit more so the the Crystalite ones. I can go 35 miles on a 48 volt 15AH Lifepo4 at an average speed of 20 MPH on a 20 inch bike.

http://www.texaselectricbikes.com/catal ... p-163.html

Hello Andy,

When I checked your link for the motor it states the motor is 12-lbs, which is 4-lbs more weight than your Puma motor. I think "Knoxie" from youtube BMS/Puma fame also mentions this lower weight too.

Why is their current motor at the above link 4-lbs heavier than yours or Knoxie's???

Thanks!

Does this motor have more torque than what the Heinzman (53 Nm rating) motor does?

[voicecoils]

Bafang PMGR no load test:

48v 8a power supply and ecrazyman older pic based 72v 28a 1000w controller used.

stand alone Cycle Analyst reports:
39.3 Km/hr
51 Volts
37 watts unloaded (.73 A)

[docnjoj]

I concur! At 42 volts nominal (48 fresh off the charger) I get about 0.9 amps with infineon and wheel with tire 20". Alot better that 12 amps with the old Crystalyte 36-72 20 amp. Never could get the motor to run well with that controller, and I tried all the combos several times. It seems unsuitable with this geared motor! Infineon works great.
otherDoc

[lfairban]

Tongxin

You didn't give a link. I believe the Tongxin motor was branded the "Nano".
http://www.nano-motor.co.uk/nanomotor.php

Thou technically it is not "geared", it has rollers that make it lighter and quieter, but the same basic idea.

I put all the information on bike kits that I have been collecting in three tables; front, front/rear, and chain/sprocket:
http://home.columbus.rr.com/lfairban/Pa ... 0Kits.html